Signaling system



Patented July 15, 1924.

nuirsn srarss isaiaar PAULB. MURPHY, or ivYaoK, NEW YORK, Assr'euoa TO wnsrnsn ELECTRIC colu- PANY, or NEW YORK, N. Y, accaron-nrroiv or NEW You-K;

SIGNALING SYSTEM.

Application filed May 4,

To aZZ whom it may concern Be it known that I, PAUL B; MURPHY, a citizen of the United States ofAmerica, re-

siding at Nyack, in the county of Rockland, State of New York, have invented, certain new and useful Improvements in Signaling Systems, of which the following is a full,-

' an alternate frequency source which does clear, concise, and exact description.

= This invention relates to a method of and means for signaling by carrier'waves and more particularly to a telegraph sys-= t em. I

It has been proposed'in radio telegraphy to use two different frequency alternating currents, recurring at a definite rate, for modulatin a high frequency wave and to transmit the modulated wave. As an alternate frequency modulating source a single vacuum tube oscillator has been provided having means, such as an interrupter or commutator, for changing the tuning of its oscillatory circuit at a definite shift frequency. At the receiving station the incoming high frequency wave is detected to yield the different frequency alternating currents which are separated by selective circuits and used to produce current impulses recurring at the definite rate or shift frequency, de termined by the commutator at the transmission station. Theseimpulses are used to control the actuation of a signal translating device through a circuit selective ofthe shift frequency or by applying them directly to a receiving device tuned to this frequency.

A particular advantage of this arrangement is that it is substantially free from interference due to strays or static; since, not only must alternating currents of the selected frequencies be employed, but in order to operate the receiving apparatus these two currents must occur sequentially at the shift frequency.

The present invention is directed to a carrier wave telegraph system employing an alternate frequency sourc for modulating a high frequency wave and transmitting the modulated wave. It is differentiated from the arrangement described above by the means employed for producing the alternate frequency modulating current at the 1921. Serial No. 466,630.

be distinguishedv from similar wave trains vice. which are a multiple of the rate of alternation of the wave trains. A still further object is to provide a system in which interference due to static and other strays is suppressed by modulating frequency. selectivity and signal tone of greater frequency than the shift frequency. An additional object is toprovide a receivingsystem in which the signal translator actuating current is of higher frequency than the shift rate.

According to this invention at the trans mitting station two oscillation generators each designed to supply a current of predetermined frequency are alternately paralyzed at a lower frequency by a control oscillator, and at the receiving station the signal translating device is supplied with impulses alternating at double the frequency of the control oscillator.

For an understanding of this invention reference may be had to the following detailed description taken in conjunction with the annexed drawings in which Fig. 1 shows a radio telegraph transmitting station and Fig. 2, a receiving station arranged in accordance with this invention. 7

Referring to Fig. 1 a three element vacuum tube oscillator l is shown having alternating current grid and plate circuits 2 and 3 coupled in feed-back relation. The frequency of the oscillations produced is determined in the well-known manner by the tuning of the closed circuit including the coupling coil a and capacity element 5. The filamentary cathode of the tube is supplied with heating current by the source 6. The source 7 supplies direct current to the plate circuit of the tube through the choke coil 8. As is well-known this coil prevents the flow of oscillating current through the As'sociated with the coils and 15 respectively.

source 7 while providing a low impedance path for the direct current supplied by this source. The alternating current path of the plate circuit includes a blocking condenser 9 and two coils 10 and 11 which are connected in series. That is, the upper terminal of coil 10 is connected to the plate; its lowerterminal, to the upper terminal of coil 11 and the lower terminal of the latter to the filament of the tube through plate winding of oscillating coil 4. V

10 and 11 are coils 12 and 13 included in the grid circuits of two vacuum tube oscillators, 14 The frequency of the alternating current supplied by the device 14 is'determined by the closed circuit consisting of the coupling coil 17 and condenser 18 included in its grid circuit. Similarly, the frequency of the alternating current generated by the device 15 is determined by the tuning of the circuit com'prising'the coil 19 and condenser 20 included in its grid circuit. Condensers 5, 18' and 20 are preferably variable. The platecircuits of these oscillators are assodated by means of the transformers 21 and 22 with the input circuit of a three-element vacuum tube amplifier 23. The plate circuit of the device 23 is coupled by a transformer 24 to the input circuit of a modulator 25 supplied with high frequency waves in any well known manner, the output circuit of which supplies high frequency modulated waves to the antenna 26. A source for supplying high frequency waves is indicated at 25. A key or other control device 27 is included in the plate circuit of the amplifier 23 to control the supply of modulating current to the modulator 25. It is to be understood that the controller 27 may be associated with the circuit system described in any other manner. Hence, it may control the oscillator 1 or either of the oscillators 14 and 15, since actuation of the receiver is dependent upon the joint action of the currents supplied by both devices 14 and 15.

The relationship of the various parts of the transmitting system and the functions of the various elements may be understood from the following description of its mode of operation. Assume, for example, that it is desired to produce a tone of 1000 cycles in the translating device at the receiving station. The oscillator 1' is designed to supply alternating current of 500 cycles and the devices 14 and 15 to generate alterating currents of say 4000 and 5000 cycles respectively. Then, when the three oscillation generators are operating the device 1 will supply paralyzing or blocking potentials alternately to the grids of the devices 14 and 15, current will flow alternately through their output circuits, and hence aloscillator 14 will be producing a current,

of minimum amplitude.

If then, the current supplied by the oscillator 1 impresses u on the input circuits of the tubes 14 an 15 an electrostatic charge of proper negative value to paralyze or block these tubes, the result will be that alternating groups of oscillations of 4000 and 5000 cycles will be impressed upon the input circuit of the amplifier 23.

This amplifier may be an intermediate amplifier or the modulator of a vacuum tube radio transmitting set and hence, when the key 27 is closed, groups of amplified 0scillations of 4000 and 5000 cycles alternating at 500 cycles will be supplied to eifect modulation of radio frequency oscillations, whereby modulated radio frequency waves will be supplied to and radiated by the antenna 26.

At the receiving station the incoming waves, modulated as described above, incident upon the antenna 28 will be detected or demodulated by the detector 29 and amplified by the amplifier 30 in any well known manner.

The output circuit of the amplifier 30 includes a tuned circuit 31 which is antiresonant to currents of 4000 cycles shunted by the primary winding of the repeating coil 33, which is connected in series with a second circuit including a tuned circuit 32 anti-resonant to trains of waves of 5000 cycles shunted by the primary winding of the repeating coil 34. The tuned circuit 31 includes a path which is of low impedance for waves of 5000 cycles, and the tuned circuit 32 is provided with a low impedance path for currents of 4000 cycles. The 4000 cycle current will therefore fiow through the path of low impedance for currents of this frequency provided in the tuned circuit 32 and the primary winding of the transformer or repeating coil 33. The current of 5000 cycles will traverse the primary winding of the repeating coil 34 and the path of low impedance therefor included in the anti-resonant circuit 31. Thus, the detected alternate frequency wave trains present in the output circuit of the amplifier 30, by the cooperation of the antiresonant circuits 31 and 32 and transformers 33 and 34,- will be separated and a1- ternately impressed upon the input circuits of the relay tubes 35 and 36. The plate circuits of these tubes respectively include amass windings 37 and38 so connected that the impulses resulting from the rectification of the alternating"frequency wave trains flow through them in opposite directions to actuate an armature associated with these windings.

Relay tube controls the supply of direct current to the relay winding 37 and the tube 36, in a similar maner, controls the relay completed from ground through the primary winding of an induction coil or transformer 41 and a source of current 42. The secondary winding of this transformer is connected to a signal translating device 43, which may be a telephone receiver.

It follows that tube 35 will be caused to respond and its space current will be changed throughout the duration of one of the alternate frequency currents and the relay 36 will similarly respond throughout the duration of the other frequency wave. The relay windings 37 and 38 will alternately attract the armature causing its contactor 39 to alternately engage the contacts 40 at a 500- cycle rate. Since an impulse of current flows from the source 42 through the primary winding of the transformer 41 each time the circuit is made and broken by the contactor 39 engaging one of the contacts 40, a tone of twice this frequency, or 1000 cycles, will be produced in the telephone receiver 43. It is to be noted that an incoming waveinodi'ilated by the signal currents of fre quencies different from that employed by the associated transmitting station willbe shunted from the transformers 33 and 34 by the filters 31 and 32 and hence the receiver will not be operated.

Again, an incoming wave radiated by a transmitting station external to this system and modulated by signal currents of the same frequencies as those to be received from the external source.

an associated transmitting station, but recurring at a rate differing from that used in this system will produce in the receiver a tone of twice the rate of change employed by Therefore, the difference between the desired signal note and that of another station under these conditions will be twice the difierencein the shift frequencies employed. This difference is more marked than would be the case if the 7 receiver were energized at the shift fre more readily distinguished.

portion of this specification.

The characteristics of the filters 31 and 32 are such that static disturbances will cause approximately equal amounts of current to pass through both primary windings of the transformers 33 and 34. Equal electrostatic charges of the same sign will be impressed upon the control elements of the relays 35 and 36 and hence currents of equal amplitude will flow through their output circuits. These currents flowing through the windings 37 and 38 in opposite directions, as described above, will neutralize one another in their effect upon the associated armature carrying the contactor 39 and the receiver will not be energized.

The relay consisting of the windings 37 and 38 and the armature carrying the contactor 39 should preferably be so adjusted that the armature will rest on the side toby the cooperating transmitting station from those emanating from other sources than in the system referred to at the beginning of this specification. Obviously this invention may also be applied to systems in which wires are used to guide the carrier waves.

By the introduction of a circuittuned to the shift frequency between the relay devices 3536 and the windings 3738, or providing the receiver 43 with a reed tuned to twice the rate of alternation of the wave trains, the present invention may obviously be modified to operate in a manner similar to the system described in the preceding While certain details and elements havebeen described for the purpose of completely'and clearly disclosing the invention, it is to be understood that this invention is not limited to the arrangement herein set forth but only by the scope of the attached claims;

What is claimed is:

1. A signaling system comprising means for transmitting a carrier wave modulated by trains of waves of different frequencies alternately recurring at a definite rate and means at the receiving station for actuating a translating device by the joint action of said wave trains at a rate different from said recurrent rate.

2. A. signaling system comprising means for transmitting a carrier wave modulated by trains of wavesof different frequencies alternately recurring at a definite rate and means at the receiving station for actuating a translating device by the joint action of said Wave trains at a rate which is a multiple of said recurrent rate.

3. A signaling system comprising means for transmitting a carrier wave modulated by signal waves of different frequencies alternating at a definite shift frequency and means at the receiving station controlled by said signal waves for actuating a translating device at double the shift frequency.

l. A signaling system comprising means for transmitting a carrier wave modulated by signal Waves of different frequencies alternating at a definite shift frequency and at the receiving station means controlled by the joint action of said signal waves for producing impulses double said shift frequency and a translating device actuated by the said double frequency impulses.

5. A signaling system comprising at the transmitting station a source of high fre quency waves, ,means for modulating said waves comprising a plurality of oscillators generating Waves of difierent frequencies and a control oscillator therefor adapted to paralyze alternately said first-mentioned oscillators and at the receiving station means controlled by the joint action of said modulatingwaves for actuating the signal translating device.

6. A signaling system'comprising at the transmitting station a source of high frequency waves, means for modulating said waves comprising a plurality of oscillators generating waves of different frequencies and a control oscillator therefor adapted to paralyze alternately said first-mentioned oscilators at a definite rate and at the receiving station means controlled by the joint action of said waves of different frequencies for actuating the signal translating device at a rate double the rate ofalt-ernation of said waves of different frequencies.

7. An alternate frequency current source comprising a plurality of continuously operative oscillators generating currents of different frequencies and a control means therefor adapted to alternately paralyze said oscillators.

8. An alternate frequency current source comprising a plurality of oscillators generating current of difierent frequencies, each oscillator including a vacuum tube device having its alternating current input and output circuits coupled in feed-back relation and a control means for alternately neutralizing the effect of the feed-back coupling of said oscillators.

9. An alternate frequency current source comprising a plurality of oscillators generating currents of'diiferent frequencies, each oscillator including a vacuum tube device having its alternating current input and output circuits coupled in feed-back relation and a control means for supplying a modulating current of sufficient amplitude to said oscillators to render them alternately inoperative.

10. An alternate frequency current source comprising a plurality of vacuum tube oscillators having coupled input and output circuits adapted to generate currents of different frequencies and a control vacuum tube oscillator adapted to alternately supply blocking potential to the input circuits of said plurality of oscillators.

11. An alternate frequency current source comprising a plurality of vacuum tube oscillators having coupled input and output circuits adapted to generate oscillations of difierent frequencies, a coil included in the input circuit of each oscillator and an alternating current source simultaneously supplying current of opposite signs of said input coils.

12. An alternate frequency current source comprising a plurality of vacuum tube oscillators having coupled input and output circuits adapted to generate currents of difierent frequencies, a coil included in the input circuit of each oscillator, an alternating current source and coils reversely connected to said sources associated with said input coils.

13. An alternate frequency current source comprising a plurality of vacuum tube oscillators having coupled input and output circuits adapted to generate currents of different frequencies, a coil included in the input circuitof each oscillator, a vacuum tube oscillator and coils included in the alternattioned oscillator associated with the input coils of the other oscillators.

14. An alternating frequency current generating system comprising two vacuum tube oscillators having coupled input and output circuits adapted to generate currents of different frequencies, a control vacuum tube oscillator generating current of frequency different from said first-mentioned oscillators and means for reversely coupling the output circuit of said control oscillator with the input circuits of the other oscillators.

15. A radio telegraph system comprising means for transmitting a carrier Wave modulated by signal Waves of different frequencies alternating at a definite rate and at the receiving station means controlled by the said signal waves for producing impulses alternating at said rate, means controlled by said impulses for producing other impulses of double said rate and a signal translating device actuated by said last-mentioned impulses.

16. An alternate frequency current source comprising a plurality of vacuum tube oscillators, each having a grid, at filament and an ing current plate circuit of said lastmen' anode and grid-filan1ent and filament-anode circuits coupled in feed-back relation to produce oscillations of different frequencies, and an alternating current source adapted to simultaneously supply potentials of opposite signs to the grids of said oscillators.

17. The method of carrier Wave signaling which comprises modulating a carrier Wave by signal currents of dilferent frequencies alternately recurring at a definite frequency, receiving the modulated carrier Wave, modifying it to produce current impulses recurring at the definite frequency and producing signal impulses of frequency greater than said definite frequency.

18. Means for generating oscillations comprising a plurality of electron discharge oscillation generators and an additional oscillation generator for controlling said generators.

19. Means for generating oscillations comprising a plurality of electron discharge 0scillation generators, an additional oscillator for controlling said generators and means associating said additional oscillator with said plurality of generators to supply oppositely directed control potentials thereto.

20. An electric apparatus comprising tWo oscillating current generators and a third oscillating current generator oppositely connected thereto controlling the operation of said first mentioned generators.

In Witness whereof, I hereunto subscribe my name this 2nd day of May A. D., 1921.

PAUL i3. MURPHY. 

